Anderton '64 reissue JTM145 - any info?

[Matec]

What is this jazzkramer?

His work was magnificent!

All we could do with this amp was made. What about the components of the attenuator, they are already proven for a long time. Its would be just another counterproof.
 
The best was, you have taken the photos, and done the checks and corrections.

I on my part, and I believe that all who participate and read this topic, just have to thank you for your dedication.

Thank you very much!

Matec.

PS. Do not forget that there are still all the other 1W ...

[jazzkramer]

Thanks Matec, I did my best. Your schema was already almost perfect.

Yesss, the other 1 W!!!! Like the JTM145, the best in my opinion!!



Bye, jazzkramer

[arjepsen]

I'm a little curious about R32 and R34.
It seems R32 is across the loudness pot, sort of making it a 500k.
But then there's also R34 pretty much going from wiper to ground, which changes the taper of the pot, if I understand correctly.
Can anyone explain why they might have made it like this??

[Littlewyan]

This is because they had to make the board work for both the JTM1 and JCM1. If you look at the standard Marshall JTM45 or 1987 Pre amp you'll see a 270k/270k voltage divider or 470k/470k in the later models coming off the wiper of the volume pot. To make the board work for both 1W amps they moved the 470k resistor bypassed by a 470pF cap before the pot then added the two 1Meg resistors in to make it pretty much the same as having the 470k/470k divider coming off the wiper.

[arjepsen]

aah... now I see.
Thanks

[Matec]

Well! Here we face a big mistake in my scheme.

R32, in JCM1 is completely visible, and its value is 1M. In photos JTM1 almost never could see clearly, the colors of the resistor, and then he remained with 1M. But in JTM1 model, there is the additional capacitor 2,2nF ...

Now in the listing of jazzkramer, this value is 10M, and a photo I had appears that this value is the same.

Yesterday, I did a test with this value in my amp, and also noticed a big improvement in the bass and midrange. The dynamics, the distortion was different, the sound grew softer.
That's it. WAS A HUGE difference. Who built the amp based on my scheme must make this change.

Sorry.

Matec

[Matec]

Hello everyone!

At this point, we have at least one reliable scheme JTM1.
This, which was checked and corrected several times.

Now, looking at the previous topics, the time is coming to discard other schemes that contains some errors.

This is the Ultimate JTM1 Schematic. (Corrected, 03/09/2014.)

[img625]http://s26.postimg.cc/k4sll6lft/JTM1_28_08_2014_B.png[/img]


(To see the full size image, click on the link above, and open in new tab)


Please confer, and check if there is any correction to be made.
If you are all right, all the pictures I posted will be replaced by this.

Thank you!

Revision "R31" on July 2, 2015

[img631]http://s26.postimg.cc/yxk7lyxhl/Jtm1_01_07_2015.png[/img]

(To see the full size image, click on the link above, and open in new tab)
Matec.

[arjepsen]

Well! Here we face a big mistake in my scheme.

R32, in JCM1 is completely visible, and its value is 1M. In photos JTM1 almost never could see clearly, the colors of the resistor, and then he remained with 1M. But in JTM1 model, there is the additional capacitor 2,2nF ...

Now in the listing of jazzkramer, this value is de10M, and a photo I had appears that this value is the same.

Yesterday, I did a test with this value in my amp, and also noticed a big improvement in the bass and midrange. The dynamics, the distortion was different, the sound grew softer.
That's it. WAS A HUGE difference. Who built the amp based on my scheme must make this change.

Sorry.

Matec

Hmm.. That's curiuos. This makes the pot value about 900k, which isn't all that far from the original 1M...
Why would they stick that 10M across, when it really doesn't change the pot value that much?

[Littlewyan]

R31 should be 1.5K. Not sure about the 10M, maybe its to help stability somehow. The 4.7M coming off V1B is probably for the same reason.

[jazbo8]

Is it just me? I can't see/download the schematic...

[Matec]

Jazbo8

You do not see the image?

The link is the own image.

Littlewyan

I talked about R32...

[jazbo8]

Jazbo8


You do not see the image?

The link is the own image.

Littlewyan

I talked about R32...

No, my ISP must be blocking the photo-sharing site - cannot access it, could someone please put it elsewhere like Dropbox, etc.
TIA

[arjepsen]

R31 should be 1.5K. Not sure about the 10M, maybe its to help stability somehow. The 4.7M coming off V1B is probably for the same reason.

well.. If I understand correctly, the 4,7M is a "ground reference" resistor.
However, the 10M is across the pot, so there already is 1M to ground...??

[arjepsen]

Hello everyone!

This is the Ultimate JTM1 Schematic.


Please confer, and check if there is any correction to be made.
If you are all right, all the pictures I posted will be replaced by this.



Matec.

Maybe you could draw those two floating circuits in another way, or make a comment by them?
I've been curious about them a couple of times, and every time I forgot, I had to go through this thread to find what they actually are

[Matec]

Arjepsen

First, I will complete the reasoning about R32.

I see, as follows:

Every time the signal leaves the motherboard, and goes to toneboard, all DC component is filtered. It would not be the case this first stage, but got anyway. As there Littlewyan said other filter formed of such C15 / R36, and JCM1 plus one, formed by C16 / R24.
I suppose that the signals with DC components,, not combine with these connectors, and cause noise, maybe ...

About these "floating" circuit.

They are a type of connection, the circuit ground with the chassis ground. I do not know exactly what the advantage of this way of making that connection. But it was common in Malhalls 90s and 2000s.

Matec